In dry or cold climates, it is often necessary to add moisture to the air inside enclosed spaces in order to maintain desired humidity levels. There are many products on the market employing a variety of techniques to increase humidity levels. Some example techniques include steam injection, water atomization, and evaporation. Evaporative humidifiers are widely used in conjunction with forced air residential and commercial heating, ventilation, and air conditioning (HVAC) systems.
Some evaporative humidifiers direct air from an air stream of an HVAC system, through a moistened humidifier pad, and back into an air stream of the HVAC system. Such humidifiers often include a housing mounted to an air duct, plenum or the like of the HVAC system. The housing typically includes an internal cavity that houses the humidifier pad, an air inlet that directs an incoming air stream from the HVAC system to the humidifier pad, and an air outlet that directs a moistened air stream from the humidifier pad and into an air stream of the HVAC system. In some humidifiers, a powered fan is provided to help force air from the air inlet to the air outlet and through the humidifier pad. In other humidifiers, such as in bypass humidifiers, a pressure differential created by the main circulating fan or blower of the HVAC system between the return air duct and the supply air duct is used to draw air from the supply air duct, through the humidifier pad of the humidifier, and to the return duct of the HVAC system.
In some cases, a controller is used to activate the humidifier. In many cases, the controller includes or is coupled to a humidity sensor that is located within the control space of the building. When the sensed humidity is below a humidity set point, the controller may provide a call for humidity signal to the humidifier. In many systems, such a call for humidity signal activates a solenoid water valve or the like of the humidifier, which when activated, allows water to flow from a water source onto the humidifier pad within the humidifier housing. When the call for humidity ends, such as when the sensed humidity rises above the humidity set point, the controller may deactivate the solenoid water valve, which prevents further water from flowing onto the humidifier pad. In many cases, a distributor tray is positioned along the top of the humidifier pad to distribute the water from the solenoid water valve relatively uniformly along the top surface of the humidifier pad. Water that passes down through and to the bottom of the humidifier pad can be collected by a collection tray and routed and expelled to a drain of the building.